Method and device for harvesting energy from ocean waves

ABSTRACT

A method and device for generating electricity from ocean waves. The device includes at least one magnetostrictive element and one or more electrically conductive coils or circuits. When the magnetostrictive element is deployed in a body of water, the motion of the body of water, including wave motion, causes changes in the strain of the magnetostrictive element. The electrically conductive coil or circuit is within the vicinity of the magnetostrictive element. A corresponding change in magnetic field around the magnetostrictive element generates an electric voltage and/or electric current in the electrically conductive coil or circuit.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/603,138, filed Oct. 21, 2009, and entitled “Method and Device forHarvesting Energy from Ocean Waves,” which is incorporated herein.

BACKGROUND

Embodiments of the invention described herein relate to a method anddevice for producing electricity by conversion of the mechanical energyof waves such as ocean waves in a water body.

Identification of new non-fossil fuel based energy sources that are bothcommercially viable and environmentally benign has become a vitaltechnological need for the next century. Such technology will not onlyfuel economic growth and contribute to global environmentalsustainability, but also reduce a nation's energy dependence on foreignoil in coming decades.

The world's oceans have long been thought of as sources of tremendousenergy, with the global capacity estimated to be around 2 terra-Watts.Successful harvesting of energy from the ocean can help to relive theload at the point of demand on some of the most heavily populatedregions of the United States. A survey conducted by the National Oceanicand Atmospheric Administration (NOAA) found that approximately 153million people (53 percent of the nation's population) lived in the 673U.S. coastal counties. Many nations around the world including theUnited Kingdom, Australia, China and India have densely populatedcoast-lines that can benefit substantially by harvesting power fromocean waves.

There are several methodologies of tapping energy from the oceans, andthese methods can be broadly divided into thermal, tidal, and wavetechniques. Of these various methods, the harvesting of wave energy isof particular importance. Within the area of wave energy harvesting,devices can again be sub-divided into on-shore and off-shore devices.Off-shore power devices tap the energy available from ocean waves usingan oscillating water column type device. Efforts to tap the seeminglyunlimited energy available through harvesting of ocean waves have provento be difficult.

Large scale efforts to tap energy from the ocean continue to be hamperedby high energy costs and low energy densities. It is estimated that theenergy cost per kW from ocean energy with conventional technologies isaround 20 cents/kWh, a level at which some form of subsidies arerequired for the technology to be widely adopted. In addition, hiddencosts include the possibility of high replacement costs in the event ofcatastrophic failure or damage during major storms.

SUMMARY

Embodiments described herein include method and device for convertingthe mechanical energy of oscillating ocean waves into magnetic andelectrical energy using a novel design that utilizes magnetostrictiveelements. Embodiments of the design combine proven concepts fromexisting technologies, such as the oscillating buoy concept used in thePelamis machine with technology proven on the bench scale for energygeneration using magnetostrictive devices to create a powerful solutionfor harvesting energy from ocean waves. Embodiments of the design areexpected to have relatively low capital costs and very goodsurvivability during strong storms. Numerical models to be developed areexpected to outline specific designs of the device capable of deliveringover 1 GW of power and perform bench scale demonstration of the keyconcept of generating electric power using a modular structurecontaining magnetostrictive elements. Some embodiments may include powermanagement strategies to optimize the delivered power from a suite ofthese devices distributed across the ocean surface.

Embodiments of the invention relate to methods for generatingelectricity. In one embodiment, the method includes utilizing the motionof a body of water, including wave motion, to cause changes in thestrain of one or more magnetostrictive elements. The method alsoincludes using a corresponding change in magnetic field around themagnetostrictive elements to generate an electric voltage and/orelectric current in one or more electrically conductive coils orcircuits that are in the vicinity of the magnetostrictive elements.

In another embodiment, the method includes utilizing the motion of abody of water, including wave motion, to cause motion of one or morebuoys, which in turn causes changes in the strain of one or moremagnetostrictive elements to which one or more buoys may be coupledmechanically. The method also includes using a corresponding change inmagnetic field around the magnetostrictive elements to generate anelectric voltage and/or electric current in one or more electricallyconductive coils or circuits that are in the vicinity of themagnetostrictive elements. Other embodiments of methods for generatingelectricity are also described.

Embodiments of the invention also relate to a device for generatingelectricity. In one embodiment, the device includes at least onemagnetostrictive element which, when deployed in a body of water, themotion of the body of water, including wave motion, causes changes inthe strain of one or more magnetostrictive elements. The device alsoincludes one or more electrically conductive coils or circuits withinthe vicinity of one or more of the magnetostrictive elements, wherein acorresponding change in magnetic field around the one or moremagnetostrictive elements generates an electric voltage and/or electriccurrent in the one or more electrically conductive coils or circuits.

In another embodiment, the device includes a buoy deployed in a body ofwater. The device also includes a magnetostrictive element mechanicallycoupled to the buoy, wherein the motion of the body of water, includingwave motion, causes motion of the buoy, which in turn causes changes inthe strain of the magnetostrictive element. The device also includes anelectrically conductive coil or circuit within the vicinity of themagnetostrictive element, wherein a corresponding change in magneticfield around the magnetostrictive element generates an electric voltageand/or electric current in the electrically conductive coil or circuit.Other embodiments of devices for generating electricity are alsodescribed.

Other aspects and advantages of embodiments of the present inventionwill become apparent from the following detailed description, taken inconjunction with the accompanying drawings, illustrated by way ofexample of the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic block diagram of one embodiment of a devicefor harvesting energy from the oscillations of ocean waves.

FIG. 2 depicts a schematic diagram of one embodiment of themagnetostrictive elements of the energy harvesting device of FIG. 1.

FIG. 3 depicts a graph of calculation results of initial analysis ofpower generation from ocean waves using one embodiment of amagnetostrictive element subjected to a cycling load employing apartially submerged buoy.

FIG. 4 depicts a schematic circuit diagram of one embodiment of anequivalent circuit diagram of several magnetostrictive elements arrangesso as to move synchronously as an ocean wavefront moves through.

FIG. 5 depicts another schematic block diagram of the energy harvestingdevice of FIG. 1.

Throughout the description, similar reference numbers may be used toidentify similar elements.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments asgenerally described herein and illustrated in the appended figures couldbe arranged and designed in a wide variety of different configurations.Thus, the following more detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thepresent disclosure, but is merely representative of various embodiments.While the various aspects of the embodiments are presented in drawings,the drawings are not necessarily drawn to scale unless specificallyindicated.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by this detailed description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present invention should be or are in anysingle embodiment of the invention. Rather, language referring to thefeatures and advantages is understood to mean that a specific feature,advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present invention. Thus,discussions of the features and advantages, and similar language,throughout this specification may, but do not necessarily, refer to thesame embodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the invention can be practiced without oneor more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments of the invention.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment of the presentinvention. Thus, the phrases “in one embodiment,” “in an embodiment,”and similar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

While many embodiments are described herein, at least some embodimentsof the invention include a method and device to capture the energy ofoscillations in ocean waves and convert this energy into electricalenergy. In this description, references to an “ocean wave” refer towaves in any stationary, moving, or oscillating body of water, and theuse of the word ocean wave in no way limits the scope or applicabilityof the invention to the ocean environment alone.

FIG. 1 depicts a schematic block diagram of one embodiment of a device100 for harvesting energy from the oscillations of ocean waves 102. Thecore modules includes a buoy 104 or buoys attached to one or moremagnetostrictive elements 106, which in turn are anchored to theseafloor or to another fixed surface or body using heavy weights 108, orby any other method. Although the magnetostrictive elements are shownattached to the buoys by rigid tethers 110, other embodiments may usenon-rigid tethers. Alternatively, the tethers may be omitted altogether,so that the magnetostrictive elements extend from the anchors to thebuoys. The term buoy, in the context of this description refers to anyphysical body that may float on or near the surface of a body of waterwhen allowed to freely do so with no forces other than its own gravityand the buoyant force applied by the water acting on the body.

Magnetostrictive materials have the property that when a strain isimposed on these materials, it results in a change in magnetization (orflux density) of an associated magnetic field. The phenomenon ofmagnetostriction has been known for over a century, but the field wasreally revolutionized by the discovery of giant magnetostrictive (Tb,Dy)alloys for use at cryogenic temperatures in the 1960s. Subsequently,giant magnetostrictive materials that work at room temperature including(Tb,Dy) and Terfenol alloys were developed. (Tb,Dy) and Terfenol-Dalloys have saturation strain values as high as 10⁻² (10,000 ppm) and2×10⁻³ (2000 ppm), respectively, allowing for the development of manypractical applications including torque sensors and high precisionactuators. Magnetostrictive materials show changes in linear dimensionswhen a magnetic field is applied (Joule magnetostriction) and areciprocal effect of changes in the magnetic properties with theapplication of stress. These characteristics make it possible to usemagnetostrictive materials to function as both actuators and as sensors.They are analogous to piezoelectric materials, but have a largeoperating bandwidth extending to low frequencies, higher energy density,and capability for higher power and force delivery. For certainembodiments of this particular application, magnetostrictive materialsare superior to piezoelectric materials due to their greater mechanicaldurability and lower production cost in high volumes.

When a wave moves through a location, the geometry outlined here, andshown in FIG. 1, results in the line tension in the magnetostrictiveelements being a strong function of the wave amplitude. While the actualgeometry of ocean waves is complex and is a cumulative summation of aspectrum of wavelets that result in changes in the effective amplitudeand frequency, for the purpose of the discussion here, waves areconsidered to be sinusoidal for simplicity. When the wave amplitude issuch that it is close to a crest, more of the buoy is submerged in waterresulting in a greater tensile load on the magnetostrictive element. Asthe wave is at a trough, less of the buoy is submerged resulting in alower tensile load on the magnetostrictive element. The geometry of theindividual magnetostrictive elements may be defined such that, for theappropriate type of buoy, the expected loads generated will result instrains that are below the saturation magnetostriction. Thus, as thewave oscillates, the extension of the magnetostrictive element follows asimilar oscillation, resulting in a constantly changing magnetic fluxdensity along the length of the magnetostrictive element. Thisconstantly changing magnetic flux density is used to generate an inducedvoltage in a coil wound around the magnetostrictive element,schematically illustrated in FIG. 2, by Faraday's law of induction,which is represented by the following equation:

ε=−n(dφ/dt),

where n is the number of turns of the coil and the term (dφ/dt) is thetime derivative of the magnetic flux, φ.

FIG. 2 depicts a schematic diagram of one embodiment of themagnetostrictive elements 106 of the energy harvesting device 100 ofFIG. 1. In the depicted embodiment, the magnetostrictive element 106includes a polymer coated copper coil 112, an external protectivepolymer sheath 114, and a magnetostrictive rod 116. The illustration ofthe magnetostrictive element and coil, shown in FIG. 2, in no way limitsthe type, orientation, structure, composition, of either themagnetostrictive element of the coil. The coil may, without limitation,be wound, suspended, printed or otherwise attached or located in thevicinity of the magnetostrictive element. The term magnetostrictiveelement simply refers to a buoy or structure, at least a portion ofwhich is constructed of materials possessing magnetostrictiveproperties. For reference, the “vicinity” of the magnetostrictiveelement refers to any location adjacent to or within the proximity ofthe magnetostrictive element which allows the coil to sufficientlyexperience the changing magnetic flux density of the magnetostrictiveelement so as to result in a measurable potential or current, forexample, greater than about 0.01 mV or about 0.01 μA, respectively. Morespecifically, the vicinity may be limited to distances at which the coilexperiences a measurable change in the magnetic flux density of themagnetostrictive element. Since the strength and profile of the changingmagnetic flux density may depend on the configuration of themagnetostrictive element, and the sensitivity of the coil may depend onthe construction and placement of the coil, the “vicinity” of themagnetostrictive element may vary from one embodiment to another.

While the buoy may be of any shape and size, in at least one embodimentthe buoys are designed such that their vertical height, or otherdimension at normal to the surface of the ocean, exceeds the expectedamplitude of oscillations of normal wave motion at a geographic locationof interest. In other words, in some embodiments, the buoy is alwayspartially submerged whether it is at the crest of a wave or the trough.In some embodiments, the system is also designed such that even as thewave is at a trough, the submerged portion of the buoy is more than whatit might have been if the buoy were floating freely—this ensures atensile load on the magnetostrictive elements through the entire rangeof motion of the buoy as the wave oscillates, and that the field changesconstantly as the wave progresses through its entire amplitude. If atany point the strain reaches a maximum (for example, the buoy is fullysubmerged), for some period of time following that, until the strainstarts to change again, the output voltage will be zero or near zero.

The fact that the generated voltage is proportional to the differentialof the magnetic flux, according to the equation presented above,provides the explanation for two statements mentioned below.

-   -   1. The maximum strain in the magnetostrictive elements should        not exceed the strain needed for the saturation magnetization        along the length of the element. If the saturation strain is        exceeded, then there is no further change in the magnetic flux        density for the period of time until the strain relaxes again        and falls below the saturation level. During this period where        the saturation strain is exceeded, the magnetic flux is constant        resulting in a zero EMF output.    -   2. The buoy may be designed such that the buoy is always        submerged more than its “equilibrium” state—i.e., the level to        which the buoy would have submerged if it were free-floating.        This ensures a constantly changing, but always tensile load on        the magnetostrictive elements. If this load were relaxed, the        strain plateaus to zero again resulting in a zero flux        differential and zero EMF.

The structure of the magnetostrictive elements is shown in more detailin FIG. 2. A core-rod of magnetostrictive material is wound with polymer(e.g., Teflon, PTFE) coated copper wire to the desired number of turns.The selection of the polymer is not critical except that the polymershould be rated to provide electrical insulation for the highest ratedvoltage expected in the coil. The wire diameter may be optimized for theintended application, as there is a trade-off between using an increasedwire diameter to lower electrical resistance of the coil that allows thedelivery or a greater voltage and higher power (lower IR losses) andusing a decreased wire diameter to lower the cost and weight of the coilitself. The external sheath can also be of the same or similar materialas the polymer coating. Alternatively, the external sheath may beanother material to provide corrosion protection of the magnetostrictiverod.

Based on the design outlined above, some embodiments may account forspecific variations in sea level due to factors such as tides forensuring that the structure continues to function as an effective powergeneration source while the external environment varies. Hence, thelocation of the buoy relative to the nominal surface of the ocean is aconsideration for the device to function effectively. Thus, seasonal anddaily tidal variations may be accounted for in the determination ofwhere to locate the buoys.

Additionally, some embodiments include a system to monitor and controlthe mean tension in the magnetostrictive elements. FIG. 5 shows oneexample of a tether controller 140 to provide such monitoring andcontrol. In one example, in high tide more of the tethers are released,and in low tide the excess length is reeled in to effectively shortenthe length. Thus the “anchor” rather than being a dead-weight may have apulley system 142 (refer to FIG. 5) and load sensors 144 (refer to FIG.5) to release or reel in the magnetostrictive elements as needed. In oneembodiment, the energy for the tension control system may be supplied bythe corresponding magnetostrictive elements and coils. Such energy maybe supplied on demand or via a storage device such as a battery 146(refer to FIG. 5).

Referring again to the construction of the magnetostrictive elements,other embodiments may use other materials. Recent research exploredductile and low field magnetostrictive alloys based on Fe—Ga, Fe—Mo, andFe—W. In some embodiments, these alloys are attractive due to theirexcellent ductility and high magnetostriction values obtained at lowapplied magnetic fields that are an order of magnitude smaller than thatneeded for Terfenol-D alloys

For this application, however, the saturation magnetization is notcritical as any magnetostrictive material can be made to work bychanging the geometry of the magnetostrictive element for theappropriate expected loading. What may be more critical are factors suchas cost and reliability as these factors directly affect the capital andoperating costs of energy harvesting device and, therefore, the cost ofthe delivered energy. The reliability requirement may be divided into amechanical strength requirement and a corrosion resistance requirement;although the latter may be less critical if appropriate protectivejackets, or sheaths, are used. As a simple comparison of Terfenol-D withalpha-iron-based alloys (Fe—Ga, Fe—Al, Fe—W and Fe—Mo), Terfenol-D is analloy or iron with terbium and Dysprosium (Tb_(0.3)Dy_(0.7)Fe_(1.9)).The high alloying levels of the relatively scarce and expensive Tb andDy makes Terfenol-D very expensive. On the other hand, α-Fe based alloysare relatively inexpensive and robust, and α-Fe based alloys provideadequate magnetostrictive behavior for this application, in certainembodiments.

FIG. 3 depicts a graph 120 of calculation results of initial analysis ofpower generation from ocean waves using one embodiment of amagnetostrictive element subjected to a cycling load employing apartially submerged buoy. Preliminary first order calculations tovalidate the concept have been carried out. The results, illustrated inFIG. 3, show that for practical geometries it is possible to obtainvoltages as high as 200 V. Also, the nature of the voltage wave-formfrom a single device results in a sinusoidal voltage output. Thisanalysis utilized a very simple model that assumed that amagnetostrictive member, with a cross-section of 2 cm×2 cm and length 2m, is subject to a sinusoidal load varying from ˜490 to ˜1145 N, loadsthat can be easily generated by partial submersion of a buoy of weight50 kg and effective density of around 300 kg/m³. This initial analysisshows that it is possible to generate an oscillating voltage with anamplitude as high as 100 V using a simple geometry for themagnetostrictive element. The geometries or numbers used in thiscalculation in no way limit the scope of the present invention and areonly intended as an example.

Since the frequency of the wave is determined by the frequency of theocean waves and is therefore relatively low (i.e., under 1 Hz), thecapacitance of the magnetostrictive elements may be ignored to developan equivalent circuit diagram as shown in FIG. 4. In particular, FIG. 4depicts a schematic circuit diagram 130 of one embodiment of anequivalent circuit diagram of several magnetostrictive elements arrangesso as to move synchronously as an ocean wavefront moves through. Bycontrolling the manufacturing process of the magnetostrictive elements,it is possible to the condition R₁≈R₂≈ . . . ≈R_(n). If themagnetostrictive elements are arranged so that they all are synchronizedto move in unison as the wave front moves along, a high power,high-voltage output can be generated. In one embodiment, the movement ofthe magnetostrictive elements may be synchronized by locating theelements in a pattern that anticipates the expected geometry of thewaveforms in a particular geographic area.

FIG. 5 depicts another schematic block diagram of the energy harvestingdevice 100 of FIG. 1. As explained above, the illustrated energyharvesting device 100 includes a tether controller 140 with one or morepulleys 142 and/or sensors 144. Although the pulleys and sensors areshown as part of the anchors, other embodiments may include pulleysand/or sensors in different parts of the overall configurations, e.g.,at the buoys, between the tethers and magnetostrictive elements, and soforth. The illustrated anchors also include batteries 146, which maystore electrical energy generated by one or more of the energyharvesting devices. In some embodiments, multiple energy harvestingdevices are coupled to a power management system 148, which combines theelectrical energy generated at each of the energy harvesting devicesinto one or more outputs with higher voltages and/or overall power.

It should be noted that the technology described herein is clean andcreates electricity from ocean waves without consuming any carbonaceousfuels or generating any harmful pollutants. Even compared with othertechnologies for harvesting ocean power, the lack of moving parts andjoints that require lubrication that may leak and pollute the oceans,this technology is exceptionally clean and environmentally friendly. Thesubstitution of the energy generated by embodiments described may hereinreduce green house gases and pollutants, compared with fossil fuels,without any undesirable side-effects or compromises. Finally, thetechnology is friendly to marine life as the structures will not resultin any significant impediment to natural migration patterns or affectsea-life in any significant way.

In the above description, specific details of various embodiments areprovided. However, some embodiments may be practiced with less than allof these specific details. Although the operations of the method(s)herein are shown and/or described in a particular order, the order ofthe operations of each method may be altered so that certain operationsmay be performed in an inverse order or so that certain operations maybe performed, at least in part, concurrently with other operations. Inanother embodiment, instructions or sub-operations of distinctoperations may be implemented in an intermittent and/or alternatingmanner. Although specific embodiments of the invention have beendescribed and illustrated, the invention is not to be limited to thespecific forms or arrangements of parts so described and illustrated.The scope of the invention is to be defined by the claims appendedhereto and their equivalents.

Although the operations of the method(s) herein are shown and describedin a particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be implemented in anintermittent and/or alternating manner.

Although specific embodiments of the invention have been described andillustrated, the invention is not to be limited to the specific forms orarrangements of parts so described and illustrated. The scope of theinvention is to be defined by the claims appended hereto and theirequivalents.

1. A device for generating electricity, the device comprising: at leastone magnetostrictive element which, when deployed in a body of liquid,the motion of the body of liquid, including wave motion, causes changesin the strain of one or more magnetostrictive elements; and one or moreelectrically conductive coils or circuits within the vicinity of one ormore of the magnetostrictive elements, wherein a surface of the one ormore electrically conductive coils or circuits is disposed at a locationaway from the surface of the one or more magnetostrictive elements todefine a gap between the surface of the one or more electricallyconductive coils or circuits and the surface of the one or moremagnetostrictive elements, wherein a corresponding change in magneticflux density in the one or more magnetostrictive elements generates anelectric voltage and/or electric current in the one or more electricallyconductive coils or circuits, wherein there is no substantial relativemotion between the one or more magnetostrictive elements and the one ormore electrically conductive coils or circuits.
 2. The device of claim1, further comprising an anchor device located in a substantially fixedlocation below a surface of the body of liquid, wherein a first end ofthe one or more magnetostrictive elements is physically coupled to theanchor device.
 3. The device of claim 2, further comprising a buoyantdevice located at approximately a liquid level that is influenced by thewave motion, wherein a second end of the one or more magnetostrictiveelements is coupled to the buoyant device, and wherein the strain on theone or more magnetostrictive elements between the anchor device and thebuoyant device changes in response to the wave motion.
 4. The device ofclaim 3, further comprising a rigid tether coupled between the one ormore magnetostrictive elements and the buoyant device.
 5. The device ofclaim 4, further comprising a tether controller to control a distancebetween the anchor device and the buoyant device, wherein the distancebetween the anchor device and the buoyant device correlates to thestrain of the one or more magnetostrictive elements.
 6. The device ofclaim 5, wherein the tether controller comprises: a load sensor tomonitor a tensile load on the one or more magnetostrictive elements; anda pulley to change the distance between the anchor device and thebuoyant device according to a target tensile load on the one or moremagnetostrictive elements.
 7. The device of claim 1, further comprisinga battery coupled to the one or more electrically conductive coils orcircuits, the battery to store at least some of the electrical energygenerated in the one or more electrically conductive coils or circuits.8. The device of claim 1, further comprising a power management systemto control power generated by a plurality of generating devices.
 9. Thedevice of claim 1, wherein each of the one or more magnetostrictiveelements exhibits a change in magnetization of an associated magneticfield in response to a corresponding change in the strain of the one ormore magnetostrictive elements.
 10. The device of claim 1, wherein eachof the one or more magnetostrictive elements comprises amagnetostrictive rod.
 11. The device of claim 10, wherein the at leastone electrically conductive coil or circuit comprises a polymer coatedcopper coil wrapped around the magnetostrictive rod.
 12. The device ofclaim 10, wherein the at least one electrically conductive coil orcircuit comprises a conductive element printed on a surface of themagnetostrictive rod.
 13. The device of claim 10, wherein each of theone or more magnetostrictive elements further comprises an externalprotective polymer sheath to substantially protect the magnetostrictiverod from corrosion due to exposure within the body of liquid.
 14. Amethod for generating electricity, the method comprising: utilizing themotion of a body of liquid, including wave motion, to cause changes inthe strain of one or more magnetostrictive elements; and using acorresponding change in magnetic flux density in the magnetostrictiveelements to generate an electric voltage and/or electric current in oneor more electrically conductive coils or circuits that are in thevicinity of the magnetostrictive elements, wherein a surface of the oneor more electrically conductive coils or circuits is disposed at alocation away from the surface of the one or more magnetostrictiveelements to define a gap between the surface of the one or moreelectrically conductive coils or circuits and the surface of the one ormore magnetostrictive elements, wherein there is no substantial relativemotion between the one or more magnetostrictive elements and the one ormore electrically conductive coils or circuits.
 15. The method of claim14, wherein a first end of the one or more magnetostrictive elements iscoupled to a substantially fixed location, and a second end of the oneor more magnetostrictive elements is coupled to a displacement locationthat changes positions in response to the wave motion of the body ofliquid.
 16. The method of claim 14, further comprising combining theelectric voltage and/or electric current from a plurality of the one ormore magnetostrictive elements to generate a higher combined outputvoltage.
 17. The method of claim 14, wherein a first end of the one ormore magnetostrictive elements is coupled to an anchor at asubstantially fixed location, and a second end of the one or moremagnetostrictive elements is coupled to the buoy, wherein the buoychanges positions in response to the wave motion of the body of liquidand causes a distance between the anchor and the buoy to change.
 18. Themethod of claim 14, wherein: utilizing the motion of the body of liquid,including the wave motion, comprises utilizing motion of one or morebuoys, which in turn causes changes in the strain of one or moremagnetostrictive elements to which one or more buoys may be coupledmechanically; and using a corresponding change in magnetic flux densityin the magnetostrictive elements to generate an electric voltage and/orelectric current in one or more electrically conductive coils orcircuits that are in the vicinity of the magnetostrictive elements. 19.A device for generating electricity, wherein the device comprises: abuoy deployed in a body of liquid; a magnetostrictive elementmechanically coupled to the buoy, wherein the motion of the body ofliquid, including wave motion, causes motion of the buoy, which in turncauses changes in the strain of the magnetostrictive element; and anelectrically conductive coil or circuit within the vicinity of themagnetostrictive element, wherein a surface of the electricallyconductive coil or circuit is disposed at a location away from thesurface of the magnetostrictive element to define a gap between thesurface of the electrically conductive coil or circuit and the surfaceof the magnetostrictive element, wherein a corresponding change inmagnetic flux density in the magnetostrictive element generates anelectric voltage and/or electric current in the electrically conductivecoil or circuit, wherein there is no substantial relative motion betweenthe one or more magnetostrictive elements and the one or moreelectrically conductive coils or circuits.
 20. The device of claim 19,further comprising an anchor deployed at a substantially fixed locationrelative to the buoy, wherein the one or more magnetostrictive elementsis physically coupled between the buoy and the anchor, wherein the wavemotion causes a distance between the buoy and the anchor to change overtime.